Talking tech with Apple's Tim Cook and Facebook's Mark Zuckerberg. Discussing US' role in Asia with President Barack Obama. And catching up with Singaporeans over a lo hei lunch.

These were just some of the highlights of Prime Minister Lee Hsien Loong's week-long visit to the United States which wrapped up on Tuesday (Feb 16, US time).

Through Facebook updates, Mr Lee has been logging his travels to San Francisco, Silicon Valley and Palm Springs, which culminated in a US-Asean summit at Sunnylands from Feb 15 to 16.

The working visit , however, was not just about serious meetings and conferences. For instance, he visited the Exploratorium, an art and science museum in San Francisco, to get ideas for Singapore's new Science Centre.

While in San Francisco, he also took a break and did some sightseeing. Photos posted on his Facebook page showed him walking a coastal trail at Lands End and visiting the Fort Mason Center Farmers' Market.

Mr Lee and his wife Ho Ching even found time to send a belated Valentine's Day greeting to Singaporeans from across the ocean.

On Feb 14, he met Singaporeans at a Chinese New Year reception and had lo hei with Singapore tech professionals in San Francisco.

He also took time off to visit the popular Ferry Plaza Farmers' Market where he tried the ham and cheese croissant from a stall recommended by his children who had lived in San Francisco.

On the first two days of his trip, he met the who's who of the US tech industry, including Tesla Motors and SpaceX CEo Elon Musk, Google chief executive Sundar Pichai, and Mr Eric Schmidt, the head of Google parent company Alphabet.

He also got to try out cool tech inventions ranging from Google's self-driving car to the Oculus Toybox.

A 360-degree video of the Facebook HQ's rooftop garden got more than 11,000 likes.

Mr Lee also posted a status update about his 64th birthday on Feb 10.

He wrote: "There is a Beatles song "When I'm Sixty-Four", and now I have got there!"